The present invention relates to a storage apparatus using a removable medium and its read/write control method. More particularly, the present invention relates to a method of shortening a mount time between mounting of a storage medium on the storage apparatus and a state in which data can be written into and read out from the storage medium.
Storage apparatuses employed in a computer system can be classified into 2 main categories. A storage apparatus in one of the categories is referred to as a removable-storage medium storage apparatus allowing a storage medium used therein to be mounted on and demounted from a drive which includes a driving mechanism, a read/write head, a control circuit and a signal processing circuit. On the other hand, a storage apparatus in the other category is known as an unremovable-storage medium storage apparatus disallowing a storage medium used therein to be mounted on and demounted. Examples of storage apparatuses in the first category are a floppy-disk drive apparatus, a magneto-optical-disc drive apparatus, a CD-ROM (Compact Disc Read Only Memory) drive apparatus and a DVD (Digital Versatile Disc) drive apparatus. An example of a storage apparatus in the other category is an HDD (Hard Disk Drive).
In recent years, the capacity of the storage device has been increasing to accompany improvements of the performance of the computer system. For example, while the storage capacity of an ordinary floppy disk is only 1.44 MB, that of a magneto optical disc is 640 MB and a DVD-RAM drive is capable of making an access to a DVD-RAM having a storage capacity of 2.6 GB on one surface. In particular, the DVD-RAM drive is not only capable of making an access to a DVD-RAM, but also compatible with storage media such as a DVD-ROM, a DVD video medium, a CD-ROM, a CD-R, a CD-RW, as well as audio and video CDs as described in an article entitled xe2x80x9cSpecial Topic I: A Growing DVD Worldxe2x80x9d in a technical magazine Toshiba Review 2, 1998, Vol. 53 NO. 2. The DVD-RAM drive is expected to be a popular and widely used future standard removable storage apparatus in the future.
Since ordinary use of a removable-storage-medium storage apparatus should not be limited to combinations of specific drive manufacturers and storage medium makers, it is necessary to keep the apparatus compatible with all manufacturers. For example, it is necessary for a drive made by A company to be capable of making accesses correctly to storage media produced by C, D and E companies. In addition, a drive made by B company must be capable of reading data written into a storage medium manufactured by A company. In order to make the DVD-RAM drive compatible with different types of storage medium and drives made by other manufacturers, a variety of adjustments are carried out when a storage medium is inserted into or mounted on the drive. The adjustments include correction of the power of a read/write laser, temperature correction and head-position correction in order for the DVD-RAM drive to learn the characteristics of the other storage media. After the learning process, the DVD-RAM is capable of executing read and write commands issued by a host computer.
In the case of a DVD-RAM drive, it takes tens of seconds to learn characteristics of a storage medium thereof since the recording density of the medium is high. Results of learning are stored in a memory of the DVD-RAM drive. The memory is generally a part of a control circuit in the DVD-RAM drive. Learning parameters are deleted when the power is turned off. When a next storage medium is mounted on the DVD-RAM drive, however, new learning parameters are acquired. In this way, a learning process is carried out each time a storage medium is inserted into the DVD-RAM drive.
In addition, the DVD-RAM drive is scheduled to keep up with a capacity enhancement of the storage medium from 2.6 GB per surface (or a double-side recording capacity 5.2 GB) for the first generation to a single-side recording capacity in the range of 4.7 to 15 GB or even larger. It is therefore difficult to shorten the time it takes to learn characteristics of a storage medium at the time the medium is mounted thereon. For this reason, a technology for shortening the learning time is demanded.
It is thus an object of the present invention to provide a method of shortening a time between the mounting of a storage medium on a storage apparatus and a state in which data can be written into and read out from the storage medium. Such a time is referred to hereafter as a mount time.
In order to achieve the object described above, a storage apparatus according to an aspect of the present invention is provided with a drive unit used for writing and reading out data into and from a removable storage medium and characterized in that the drive unit controls operations to write and read out data into and from the medium in accordance with an external parameter. It is desirable to provide an external parameter for letting the drive unit adapt itself to the temperature of an environment in which the drive unit is operating.
According to another aspect of the present invention, there is provided a storage apparatus having a plurality of drive units. The storage apparatus further has a plurality of slots each used for accommodating a storage medium, a transport unit for conveying a storage medium between the slots and the drive units and a control unit for controlling the transportation of a storage medium between the slots and the drive units. It is desirable to provide a control unit having a memory for storing a parameter for controlling operations carried out by any of the drive units to write and read out data into and from a storage medium mounted thereon for each combination of any of the drive units and any of storage mediums accommodated in the slots. In such a configuration, the control unit transfers a parameter proper for a combination of a drive unit and a storage medium mounted thereon to the drive unit. A storage medium can be identified individually by the slot for accommodating the medium. As an alternative, a storage medium can be identified from identification information recorded on the medium or on an identification means provided on a tray on which the medium is mounted.
According to a still another aspect of the present invention, there is provided a computer system comprising a computer and a storage apparatus wherein the storage apparatus includes a plurality of drive units, a plurality of slots each used for accommodating a storage medium, a transport unit for conveying a storage medium between the slots and the drive units and a control unit for controlling the transportation of a storage medium between the slots and the drive units; whereas the computer has a parameter for controlling operations carried out by any of the drive units to write and read out data into and from a storage medium mounted thereon for each combination of any of the drive units and any of storage mediums accommodated in the slots.
When a storage medium is set in a specific one of the drive units, the computer supplies a parameter proper for a combination of the storage medium and the specific drive unit to the unit. Then, the drive unit carries out operations based on the parameter to write and read out data into and from the storage medium mounted thereon.
Other features and advantages of the present invention will be apparent from the description of the preferred embodiments and from the claims.